1. Field of the Invention
The present invention relates generally to aligning optical elements, and particularly to a bonded alignment structure for optical elements.
2. Technical Background
In the assembly of optical devices it is often desirable to use free space optics to allow two optical elements to engage in optical communication with one another. Each optical element may be thought of as having an optical axis. In order for the optical elements to engage in efficient optical communication with one another the optical elements must be optically aligned with one another. Typically optical alignment consists of aligning the optical axes of two or more optical elements so that an optical signal following a desired optical path through the optical elements possesses certain characteristics. Optical alignment requires rotating and translating the optical elements in 3-space to bring their respective optical axes in to a predetermined degree of alignment. For example, placing a lens in the path of a laser beam so that the lens performs an optical operation, such as collimating or focusing, on the laser beam.
Alignment and structural attachment of miniature photonic optical elements, including lenses, mirrors and fibers, has proven difficult. Many optical elements have optical tolerances that are sufficiently large enough to allow passive alignment of the optical components. The optical tolerances of many optical elements, however, are too small to allow passive alignment. The assembly of these optical elements into optical devices requires active alignment. Active alignment may be defined as placing at least two optical elements in optical communication with one another and repositioning at least one of the optical elements until some characteristic of the optical signal has a predetermined value. Typically, active alignment is accomplished by moving one of the optical elements relative to the other optical elements while measuring the intensity of the optical signal received by one of the optical elements.
The active alignment process may be complicated by the fact that the structural assembly must allow the optical elements to be both aligned and fixed in place without inducing unacceptable shifts in location of the optical element. Active positioning is comparatively expensive and is often difficult to implement due to the limited space inside photonic packages. Captive positioning is desirable, but designs often require a high degree of mechanical complexity and have relatively large tolerances.
There is a need for a relatively simple captive alignment structure capable of obtaining the tight tolerances necessary for optical alignment while minimizing the shift in location of the optical components during attachment.
The present invention is directed towards methods and structures for mounting optical components that require active alignment.
One embodiment of the present invention is a method for mounting an optical element using five (5) Cartesian degrees of freedom. The method for mounting an optical element includes the step of selecting an optical element to be mounted for optical communication with another optical element. The method also includes the step of coupling the optical element to a submount. The method further includes forming a mounting assembly by selecting a support block having at least two non-coplanar surfaces and coupling the support block to the submount. The optical element is then positioned for optical communication with another optical element by selectively manipulating the position of the submount and the support block to align the optical element with at least one other optical element. The relative position of the submount and the support block with respect to the other optical element are then fixed.
In another embodiment, the present invention includes a mount for an optical element. The mount includes a support member having an anchor surface slidable on a substrate and a alignment surface at an angle to the anchor surface. The mount further includes a submount having a bonding surface and a mounting surface. The bonding surface and the mounting surface are at an angle to one another. The bonding surface is coupled to the alignment surface of the support block and the optical element is coupled to the mounting surface of the submount.
In another embodiment, the present invention includes a mount for an optical element. The mount includes a submount and two support blocks. The submount has two parallel surfaces and the two support blocks are placed to slidably engage the two parallel surfaces. The optical element is coupled to the submount. The submount and two support blocks are arranged so that the submount is rotatable about an axis perpendicular to the two parallel surfaces and is translatable in a plane parallel to the two parallel surfaces. The optical element is positioned to engage in optical communication with at least one other optical element by selectively rotating the submount about two non-parallel axes and translating the submount in three orthogonal directions.
One advantage of the present invention is that it provides a mount for an optical element adjustable in five (5) degrees of Cartesian freedom.
Another advantage of the present invention is that the adhesive bonds may be thoroughly cured without thermal distortion.
Another advantage of the present invention is that it has a relatively low vertical profile which is important in the packaging of active opto-electronic devices.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.